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Various military aircraft just flew overhead on their way to the Trooping of the Colour in London.

At the same time, my Television's signal went completely dead, and then restored once they had gone. (It's a table top arial, but usually manages to get a decent signal.)

Is this a coincidence, or would they be jamming similar frequencies?

They were several helicopters, and according to what I can find, they were:

Juno HT1 - x3
Wildcat HMA2 & Merlin HM2 - x2
Wildcat AH1 & Apache - x4
Wildcat AH1 & Merlin Mk4 - x2
Chinook x3 & Puma HC2

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  • $\begingroup$ I remember as a kid in the late 1960s/early 1970s that any time any helicopter flew over our house, the TV would become a staticky mess. This was true for all helicopters, including civilian. As tuner electronics improved in quality in the early 80s, it seemed to subside and not happen any more. From the early 80s on my TVs were always cable fed, so it never happened to me again. $\endgroup$
    – Max R
    Jun 18, 2023 at 4:03
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    $\begingroup$ I grew up in London in the 1960 with analog black and white TV on VHF and a rooftop antenna. When planes went over the picture could 'flutter' due to reflections from the aircraft metal fuselage and wings rapidly adding to and subtracting from the signal and the TV set automatic gain control being unable to keep up. Later on UHF this got better. With digital over-the-air TV you wouldn't get this fading - the way a modern set works you either get a perfect picture or nothing. A TV with a marginal set top antenna could be OK most of the time and just give up when the signal got degraded. $\endgroup$ Jun 18, 2023 at 13:40
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    $\begingroup$ As previously commented, a reflection of the signal by the aircraft is likely to be the cause. Even though DVB-T is designed against echo by using a guard interval between symbols, it has a limit. You would know if you're close to the limit by looking at the BER, bit error ratio. Any value larger than $\small 2 \times 10^{-4}$ indicates little margin for degradation. $\endgroup$
    – mins
    Jun 19, 2023 at 13:22

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It’s unlikely that they would be deliberately jamming TV signals - what’s the benefit apart from drawing additional attention to their presence? All types of radio receivers, including TV, are to some degree sensitive to out-of-band signals, so any sufficiently powerful transmitter using a different frequency band could cause problems, depending on how good your receiver is at rejecting unwanted noise. A ‘bunny ears’ antenna on top of a TV set is likely to be quite vulnerable. Military aircraft will be using radar, transponders, airband radio and so on, so there’s a good chance that one of those could cause interference.

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  • $\begingroup$ I accept that there's little military benefit in stopping people from watching TV; I thought perhaps that those frequencies might have a role in something else. But consequential interference through other frequencies may well be sufficient, as you point out. Thanks! $\endgroup$
    – benwiggy
    Jun 18, 2023 at 11:57
  • $\begingroup$ @benwiggy There is little military benefit in stopping friendlies from watching TV during peacetime... $\endgroup$
    – T.J.L.
    Jun 20, 2023 at 12:19
  • $\begingroup$ @T.J.L. True., which is why I though it might be incidental. Mind you, friendly civilian populations have endured worse for no strategic gain.... $\endgroup$
    – benwiggy
    Jun 20, 2023 at 14:55
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The electronic warfare transmitters, jammers, are seldom turn on during routine flights. While I know little about such facilities in the UK, in the USA there are several ranges designed to test the equipment with transmitters for them to jam.

Even when performing maintenance tests, we had to be careful as certain civilian systems could potentially be affected, especially if the transmitters were not exactly on frequency or had bandwidth issues.

If blocking them was needed for some reason, some aircraft certainly do carry equipment that could have interfered with broadcast TV signals.

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